Abstract
Kinetics of MnO4--thiourea redox reaction have been investigated spectrophotometrically in presence of cationic micelles of cetyltrimethylammonium bromide (CTAB). Upon mixing aqueous solutions of permanganate and thiourea, a readily distinguishable brown colour appears and then disappears slowly. Various experiments have been performed to confirm the nature of brown colored solution. The effects of [MnO4-], [thiourea] and [H+] on the reaction rate were determined in presence of CTAB (=8.0 x 10(-4) mol dm(-3)). Absorbance of the reaction mixture increases with [CTAB] which suggest the incorporation/association of permanganate with the head group of CTAB micelles. Menger-Portnoy model was used to explain the effect of CTAB micelles. The reaction proceeds through the fast formation and slow decomposition of water-soluble colloidal MnO2 as an intermediate. A suitable mechanism is proposed for the oxidation of thiourea by permanganate. (c) 2007 Elsevier B.V. All rights reserved.